The invention relates to a control unit for a terminal of a digital, cordless telecommunication system for delivering control signals to further units of the terminal, as well as to a method for such a control unit.
The communication between the terminals of a digital, cordless telecommunication system, notably between handsets and base stations, takes place via a radio control unit which is connected to an antenna in each terminal. The typical construction of a terminal is shown in FIG. 1. The radio control unit 2 therein is controlled by a control unit 1 (BMC: Burst Mode Controller). The control unit 1 is responsible for the time-critical processing of the data to be transmitted and received. Moreover, it outputs control signals via the control leads of the radio control unit 2. The control unit 1 itself is controlled by a microcontroller 3 which carries out the protocol functions and other, less time-critical functions. In addition, a further unit 4 may be provided for some systems, for example, for systems involving the transmission of audio data, which further unit carries out digital signal processing of the data to be transmitted or of the received data. Finally, the microcontroller 3 and the unit 4 for the digital signal processing have access to the applications 5 of the terminal.
FIG. 2 shows the construction of the control device 1 in greater detail.
The main components of the control device 1 are formed by a control unit 10 and a data processing unit 11. The control unit 10 receives commands 20 from the microcontroller 3; in conformity therewith it controls the output of control signals 22, via control leads, to the radio control unit 2 and generates and outputs control signals 23 for the data processing unit 11. Moreover, the data processing unit 11 supplies the control unit 10 with feedback information 24 which can also influence the control behavior of the control unit 10. The data processing unit 11 itself is used to perform given functions on the data bits 27, 29 received and the data bits 26, 28 to be transmitted, for example, encryption (scrambling) 12, 14, or generating a test sum 13 (CRC: Cyclic Redundancy Code). In a terminal of a digital cordless telecommunication system, for example, DECT, the data to be transmitted and received must be processed in real time. The control unit 10 and the data processing unit 11 can both apply status information 21, 25 to the microcontroller 3.
The control unit of a control device is typically implemented as a hardware automatic. Therefore, problems are encountered as soon as a modification of the output of the control signals is required. For example, any change of format of the data packets necessitates a new design of the control unit, even when the same data processing functions are to be used and merely a different bit timing is desired. Similarly, the addition or removal of data processing functions as well as a modification of the specification of the radio interface or the timing for the radio control signals also necessitate a new design of the control unit. Consequently, the hardware of a control unit for a given telecommunication standard, for example DECT, can be used for other telecommunication systems, for example the United States ISM band system, only at the expense of major adaptations.
From GSM, however, a baseband control unit is known in which the hardware implemented automatic for the output of control signals is dispensed with. The unit used instead is illustrated in FIG. 3: a microcontroller writes values for an event containing control signals into a control signal register 30 and writes the values for an instant at which the control signals of the event are to be output via the control lines 36 connected to the control signal register 30 in an instant register 31. A comparator 32 continuously compares the instant of the instant register 31 with the time delivered by a timer 32. The timer 32 is controlled by a local clock generator 35. In the case of correspondence, the event is output from the control signal register 30 via an output register 34 and the control lines 36. The control lines may supply, for example, a radio control unit with control signals 38 and also apply control signals 37 to a data processing unit.
The time settings and the occupancy of the control lines thus can be selected completely at random, because the tasks of the hardware automatic were transferred to the software. Because of the use of the registers it is not necessary either for the software to imitate the actions of the hardware automatic bit by bit.
This offers an advantage, for example, when the format of data packets changes. Because the instants for transferring control signals from the control unit to the data processing unit are preset by the software, a change of format can be dealt with by way of a software modification which is far less intricate than a new design of the hardware. The addition or removal of functions of the data processing unit can also be realized by simple changes in the allocation of the individual bits of the registers to the control lines from the control unit to the data processing unit. Newly allocated significance contents and changed output times for the control lines can thus be maintained by way of pure software modification. The significance contents, the timing and the levels of the radio control signals can also be completely preset by the software, so that modifications are also possible for the radio interface without directly necessitating a new design of the hardware.
An appropriate proposal for a GSM mobile radio apparatus can be found, for example in the publication DE 197 47 275 A1.
The control units that are known from the GSM application, however, cannot be simply transferred to applications in the digital, cordless field. For example, applications such as DECT have a bit rate of 1152 kbit/s which is significantly higher than that of GSM in which the bit rate is 270 kbit/s. Moreover, DECT requires the simultaneous support of a plurality of connections. This leads to a significant amount of software processing and to real-time requirements that can hardly be met at present. For example, in the worst case a reaction time of less than the time of a bit, so less than 0.87 xcexcs, is required. Because of the need for a minimum delay during the processing in cordless systems connected to PSTN (Public Switch Telephone Networks), on the other hand xe2x80x9coff-linexe2x80x9d processing of the data received, so processing not in real time, is not possible. Finally, processing steps such as encryption and checking of a test sum etc. must be performed on the data received immediately and with the timing of the signal data received. Therefore, the use of a reference time which is dependent on the local system time (as used for GSM) is not possible either.
It is an object of the invention to provide a flexible and energy-saving control unit for a terminal of a digital, cordless telecommunication system for delivering control signals to further units of the terminal. It is another object of the invention to provide a method enabling the use of a flexible and energy-saving control unit for a terminal of a cordless telecommunication system.
The object according to the invention is achieved by means of a control unit.
The object is also achieved by means of a method of using the control unit.
The control unit according to the invention and the method according to the invention are based on software control with adequate hardware support, resulting in a high flexibility while ensuring at the same time that no excessive requirements are imposed on the microcontroller performance.
The invention enables adaptations to changing secondary conditions without necessitating a new design of the hardware. It is thus simply possible to perform an adaptation to applications of different systems by appropriately adapting the events and instants delivered to the register arrays by the microcontroller. Similarly, it is possible to react to changes in units connected to the control lines, for example changes in an interface or a data processing unit, for example, when the occupancy of control line or the timing and the signal levels at the radio interface are to be changed.
Despite the increased flexibility, as a result of the use of the register arrays the invention can also be used in systems with high data rates, such as DECT, without imposing major demands on the software, because the microcontroller can load a plurality of commands at the same time and hence need not respond within the time of a single bit, so that the real-time requirements can be more readily satisfied.
Preferred embodiments of the control unit according to the invention and preferred versions of the method according to the invention are disclosed in the dependent claims.